// https://www.lintcode.com/problem/maximum-depth-of-binary-tree/my-submissions
// 97. Maximum Depth of Binary Tree
// Given a binary tree, find its maximum depth.

// The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

// Example
// Given a binary tree as follow:

//   1
//  / \ 
// 2   3
//   / \
//   4   5  
// The maximum depth is 3.

/**
 * Definition of TreeNode:
 * class TreeNode {
 * public:
 *     int val;
 *     TreeNode *left, *right;
 *     TreeNode(int val) {
 *         this->val = val;
 *         this->left = this->right = NULL;
 *     }
 * }
 */

class Solution {
public:
    /**
     * @param root: The root of binary tree.
     * @return: An integer
     */
    int maxDepth(TreeNode * root) {
        if (!root)
        {
            return 0;
        }
        return max(maxDepth(root->left), maxDepth(root->right)) + 1;
    }
};